A Comparative Study of Invasive and Micro-Invasive Analytical Methods for the Detection and Identification of Historically Applied Pesticides to Archival Records

The National Archives UK has previously carried out invasive sampling and analysis on records in its collections which were found to contain various organochlorine pesticide (OCP) residues on all tested items regardless of format or period of creation. This study presented a rare opportunity to carry out comparative research of invasive and swab sampling methods on original, historic materials for the detection and identification of hazardous substances. Swabbing was carried out on the same records that had been invasively sampled to determine the sensitivity and applicability of this method relative to invasive sampling as well as the likelihood of pesticide transfer during handling of the records. Analysis by gas chromatography -mass spectrometry (GC-MS) demonstrated that the presence of a number of pesticides could effectively be identified using a dry swabbing method, including pentachlorophenol, ortho-phenylphenol, and the breakdown products of DDT and methoxychlor. The pesticides identified in invasive and swab testing from the same book were sometimes different, highlighting that the method of sampling will affect the results. Our results from this case study provide a snapshot, comparing the concentrations of hazardous organic pesticides detected in the invasive tests versus those found in swabs, and compare these quantities to human health-based screening concentrations. We argue that a dry swabbing programme is a good option in archival settings for screening for a comprehensive suite of pesticides, complementing existing occupational health approaches that take into account a whole collection, and can provide information to facilitate access and handling of historical records.